The back flap of the dust jacket is not shown in its entirety, so the lack of a copyright notice is not certain. However, at least one different dust jacket featuring the same cover art, but from a different printing, is known to be published without a copyright notice.
Note that it may still be copyrighted in jurisdictions that do not apply the rule of the shorter term for US works (depending on the date of the author's death), such as Canada (50 p.m.a.), Mainland China (50 p.m.a., not Hong Kong or Macao), Germany (70 p.m.a.), Mexico (100 p.m.a.), Switzerland (70 p.m.a.), and other countries with individual treaties.